1. Field of the Invention
The present invention relates generally to a device and method for heating a semiconductor wafer. More particularly, this invention relates to a heating chamber suitable for use in a reflow process to form a metal wiring having a multi-layered wiring structure. This invention also relates to a method of heating a wafer using the heating chamber.
2. Description of Related Art
High-density and highly integrated semiconductor devices usually require multilayered metal wiring. Metal wiring is used to transmit electrical signals and an electrical resistance thereof must therefore be kept to a minimum. The metal wiring must also be economical and highly reliable. Aluminum is widely used to form the multi-layered wiring so that these requirements can be satisfied.
When using aluminum, it is important to completely fill a contact hole for connecting a device on a lower layer of a semiconductor substrate and aluminum wiring on an upper layer. Via holes for connecting aluminum wiring on a lower layer and aluminum wiring on an upper layer must also be completely filled with a metal material to electrically connect the wirings to each other. Aluminum can also be used as the metal material for filling the contact or via hole (collectively “contact holes”) because it is fairly inexpensive and has excellent conductivity. Various process techniques have been used for filling a contact hole with aluminum.
While fabricating a next-generation memory device with wiring having a width of 0.25 mm or less, for example, a contact hole having a large aspect ratio is filled with aluminum. A chemical vapor deposition (CVD) process with excellent step coverage is used to form an aluminum liner in the contact hole. An aluminum film is then formed on the aluminum liner using a physical vapor deposition (PVD) method such as sputtering. The resulting aluminum structure is then heated to produce enough energy to cause the aluminum film to reflow. As a result, a contact having no void is formed. During this process, it is important to constantly maintain the desired heating temperature to cause reflow of the aluminum film. Constantly maintaining the heating temperature provides uniformity and reproducibility to the process of forming the metal wiring. Unfortunately, however, in conventional wafer heating processes, a significant amount of time is required to raise the temperature of the wafer to a desired process temperature in a heating chamber.